In operation, internal combustion engines discharge heat energy into the external environment through exhaust gas, engine cooling systems, charge air cooling systems, etc. The discharged heat energy that is not used to perform useful work is typically known as “waste heat.” Waste heat recovery systems capture a portion of the waste heat to perform useful work, such as generating electrical energy via an expander (e.g., a turbine). Some waste heat recovery systems utilize a Rankine cycle. The Rankine cycle is a thermodynamic process in which heat is transferred to a working fluid in a Rankine cycle circuit. The working fluid is pumped to a boiler where it is vaporized. The vapor is passed through an expander and then through a condenser, where the vapor is condensed back to a fluid. The expander may drive a generator to generate electrical energy, or transfer mechanical energy through a belt drive to engine crankshaft. An organic Rankine cycle is a Rankine cycle in which the working fluid is an organic, high molecular mass fluid with a liquid-vapor phase change (boiling point) at a lower temperature than that of water. Such a fluid enables heat recovery from relatively lower temperature sources relative to other Rankine cycle systems.